1. Field of the Invention
The present invention relates to a ball bearing device for supporting a rotary shaft of a rotating machine such as a generator for cars. More particularly, it relates to a ball bearing device to improve waterproof property of the bearing part.
2. Description of the Prior Art
FIGS. 1 to 3 show a typical generator for cars and a conventional waterproof ball bearing device applied to such generator, in which a reference numeral 1 designates a stator of an a.c. generator; a numeral 2 designates a rotor; a numeral 3 designates a front bracket integrally attached to the stator; and a numeral 4 designates a ball bearing mounted on the rotary shaft 7. The ball bearing 4 comprises an inner ring 41, an outer ring 42, a plurality of balls 43 held between the both rings and rubber-sealing plates 44a, 44b for sealing both sides of the balls 43. The rubber-sealing plates 44a, 44b have their one ends connected to the outer ring 42 without any gap and their other ends extending to the inner ring 41 with a space of gap or being in contact with it under a slight pressure. A numeral 5 designates a retainer fixed integrally to the front bracket 3 to support the bearing 4; numerals 8a, 8b designate spacers mounted on a rotary shaft 7, the former 8a being interposed between the rotor 2 and the bearing 4 and the latter 8b being interposed between a pulley 9 and the bearing 4. Between the bearing 4 and each of the spacers, sealing means 6, 6 made of metal are respectively interposed to cover the end of the each of the rubber-sealing plates 44a, 44b at the side of the inner ring 41 to thereby improve waterproof property of the bearing.
In the a.c. generator for cars having a bearing constructed as above-mentioned, water invades the bearing 4 through the gap between the front bracket 3 and the retainer 5 as shown by an arrow mark a to deteriorate a lubricating agent in the bearing whereby the life time of the bearing is shortened.